1. Field
Exemplary embodiments relate to an etchant composition, and a method of manufacturing a display substrate using the etchant composition. More particularly, exemplary embodiments relate to an etchant composition used for etching a metal layer including copper, and a method of manufacturing a display substrate using the etchant composition.
2. Description of the Related Art
Generally, a display substrate used in a display apparatus includes a thin-film transistor (“TFT”) as a switching element for driving a pixel, signal lines connected to the TFT, and a pixel electrode. The signal lines include a gate line transmitting a gate driving signal and a data line transmitting a data driving signal.
As the size of display apparatuses increases and the resolution is improved, the length of the gate and data lines is increased while at the same time the width of the gate and lines is decreased, and as a result electric resistance is increased. Thus, a resistance-capacitance (“RC”) signal delay is caused. In order to solve this RC signal delay problem, gate and data lines are formed from a metal having relatively a low resistance. Copper is a metal having relatively a low resistance and when used for forming gate and data lines has excellent electric conductivity and has a resistance much lower than aluminum or chrome. Furthermore, copper is relatively abundant as a natural resource. However, the resistance of copper against an oxidizer is greater than that of aluminum or chrome, so that a stronger oxidizer is desired for etching a copper layer when forming signal lines, as compared to aluminum or chrome.
Copper etchants that include a strong oxidizer are effective for etching the copper layer, however, patterns previously formed in prior processes may be easily damaged from such a copper etchant. A conventional peroxide-based etchant is sometimes replaced with an etchant including a persulfuric acid-based compound as a main etching element to reduce etching of patterns previously formed in prior processes when etching the copper layer. However, such an etchant is unstable when stored at a room temperature, and has a limitation to maximize a number of substrates treated by the etchant.
Furthermore, a signal line having an increased thickness is used in order to increase a response speed of a display device, copper wiring formed using a conventional etchant has a small taper angle thereby reducing an opening ratio of a display device. Thus there remains a need for an improved etchant.